Winch and Boom Systems of Marine Deck Cranes: The Ultimate Test of Seawater, Salt Spray and Heavy Loads — SAVI Bearings Run Maintenance-Free in Marine Environments

Products used: EPH corrosion-resistant sliding bearings + CRG filament-wound bearings

Application positions: Winch drive shaft bearing housings, boom hinge joints, hook block sheave assemblies, slew bearing bushings

Operating requirements: Seawater and salt spray corrosion resistance, heavy loads, maintenance-free operation, UV resistance, low water absorption

Customer Background

A ship equipment manufacturer specializing in marine deck cranes and hoists, with products installed on the decks of fishing vessels, workboats and passenger ships, with lifting capacities of 3–25 t. Marine cranes are long-term exposed to the extreme environment of seawater splash, salt spray, ultraviolet light and wave-induced motion. The company exports to Southeast Asia, the Middle East and Europe, and has extremely high requirements for after-sales service and maintenance costs — bearing failures on ocean voyages are almost impossible to replace on site.

After successful adoption, bearing life was extended from 8 months to more than 5 years, annual maintenance costs were reduced by 82%, and environmental pollution was reduced to zero.

Problem Description

The marine crane previously used bronze-graphite bearings and stainless steel needle roller bearings, which caused numerous problems in the marine environment:

Seawater corrosion causing bearing seizure. Salt spray and seawater splash come into direct contact with the bearings. Bronze bearings develop severe corrosion pits within 3–8 months, and even stainless steel bearings cannot fully resist chloride ion corrosion. Once the bearings seize, the boom cannot slew and lifting operations are forced to stop.

Lubricating oil polluting the ocean. Metal bearings require periodic application of grease, and the lubricating oil disperses in seawater, polluting the marine environment and violating the environmental protection requirements of the IMO MARPOL Convention.

Difficulty of maintenance on remote voyages. Ships sail for weeks or even months at sea, and deck cranes cannot be serviced or receive replacement parts during the voyage. A bearing failure means catches cannot be lifted or cargo cannot be loaded and unloaded — causing enormous economic losses.

Solution

SAVI provided the marine crane manufacturer with a systematic solution using three products:

Winch drive shaft bearing housings use CRG filament-wound bearings, which are formed by winding high-strength glass fiber with corrosion-resistant engineering plastic. With a compressive strength of up to 200 MPa, they neither corrode nor swell from water absorption when immersed in seawater (water absorption <0.3%), and can withstand lifting forces of up to 25 t.

Boom hinge joints and slew bearings use EPH corrosion-resistant engineering plastic sliding bearings. This material is specially designed for marine environments, offering long-term resistance to salt spray, seawater and UV radiation, with a continuous operating temperature of up to +200°C. BAL plastic spherical plain bearings are installed at the boom hinge points to compensate for installation deviations and hull deformation, ensuring smooth boom motion amid wave-induced motion.

The recommended shaft materials are 316L stainless steel or hard chrome-plated steel; when paired with EPH, the friction coefficient is 0.07–0.20. Each marine crane uses 14–20 SAVI bearings. All materials contain no liquid grease, fully complying with the MARPOL Convention's requirements for marine environmental protection.

Customer voice: "Our cranes are mounted on ship decks — once they leave port, they're gone for months. Our worst fear used to be hearing from customers that the crane couldn't rotate, which almost always meant the bearing had rusted solid. Since switching to SAVI plastic bearings, there has not been a single bearing failure report in five years. And with no more greasing, we also passed the classification society's environmental inspection."

Customer Benefits

• 5 years of maintenance-free operation: The EPH + CRG combination runs stably in seawater environments for more than 5 years.

• 82% reduction in annual maintenance costs: Labor and spare-part costs for periodic greasing, disassembly and replacement eliminated.

• Zero marine pollution: No lubricating oil exudation, compliant with MARPOL environmental requirements.

• Salt spray resistance without rusting: EPB10 and CRB-4 materials show no corrosion after long-term immersion in 3.5% saltwater.

• UV aging resistance: UV stabilizers added to the materials; performance does not degrade after 5 years of outdoor exposure.

• Zero failures on remote voyages: 0 bearing failure reports in 5 years, with extremely high customer satisfaction.

Comparison Data